Heat Pipe with Inner Zeolite Coated Structure

ABSTRACT

The heat pipe comprises a shell and an inner zeolite coated structure. The shell has an inner surface. The inner surface surrounds an enclosed chamber. The chamber is partially filled with a working fluid in a vacuum. The working fluid may be changed into a liquid phase or a gas phase by following temperature change. The coating material comprises a zeolite, a binder and an additive. The material is sintered on the inner surface of the heat pipe. Consequently, the zeolite coating is formed between the inner surface and the enclosed chamber. Thus, the present invention uses a porous material of zeolite with pore size smaller than grooves and meshes to have excellent evaporation heat transfer and capillary force. The zeolite coating of the present invention does not fail without air isolation. The present invention is inner manufactured under atmospheric condition so has no size limitation.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to the inner structure of heat pipe; moreparticularly, relates to the heat pipe with zeolite coated on the innersurface for capillary wick for cooling and waste heat recovery.

DESCRIPTION OF THE RELATED ARTS

Heat pipe is most commonly used in the following fields: cooling ofelectronic components and electrical devices, and waste heat recovery ofequipment or machinery. Currently much waste heat is discharged directlyor indirectly without recycling. Directly-discharged waste heat mostlyexists in the exhausted gas and liquid, and its sources include boilers,burners, incinerators, furnaces, combustion engines and other heatingfacilities. Indirect-discharged heat sources are the cooling air orcooling water loops that are used to remove the heat of facilities forprotection, or the heat of processes for next handling station.

The first prior art in FIG. 7 is a thermosyphon 100. The shell 101 ismade of metal and partially filled with working fluid 102 inside afterbeing vacuumed. When the evaporator section 103 is heated by heat sourceat lower position, the liquid working fluid 102 evaporates by absorbingheat and turns into gas. The gas working fluid 102 of high pressure isinstantly formed and by buoyancy rushes upwards the condenser section104 at higher position. There, the gas working fluid 102 condenses byreleasing heat to outside and turns into liquid. The liquid workingfluid 102 flows downwards the evaporator section 103 along the wall bygravity, and after that absorbs heat again. Such a cycle repeats totransfer heat from the lower position to the higher position. Yet, it isobvious that thermosyphon can only transfer heat upwardly.

In the case of the amount of the liquid working fluid flowing back tothe evaporator section is reduced, the evaporator section would dry out.Hence, a second prior art that heat pipe which a capillary wick is builtinside and attached to an inner surface is proposed. With the wick,capillary force is provided to enhance the liquid working fluid to flowback. The wick is obtained by sintering a powder of at least one of thefollowing metals: copper, aluminum, zinc, lead, tin, nickel, silver, andgold. However, the metal powder must be sintered under a vacuum or inertgas filled circumstance. Besides, the overall length of the heat pipe islimited by the size of the sintering furnace so it is only suitable fora heat pipe with a length less than 50 centimeters (cm). In addition,air isolation is required after sintering; otherwise the wick may beeasily oxidized and fail.

For other prior art, a capillary wick inside the heat pipe with a lengthmore than 50 cm can be made by a fiber of the material compatible withworking fluid. The fiber may be further woven into various forms of meshto be placed inside the heat pipe. Otherwise grooves are formed on theinner surface of the heat pipe. Although the above method suits varioussizes of pipe, the pore size is too big so that the evaporation heattransfer capability and capillary force is insufficient.

The other prior arts relates to the inner structure of heat pipe includeU.S. Patent US2013/0168052A1, US2013/0160976A1, US2010/0200199A1, U.S.Pat. No. 7,594,573B2, US2006/0222423A1, US2006/0207750A1,US2006/0016580A1, US2005/0116336A1, U.S. Pat. Nos. 7,086,454, 4,674,565,3,952,798, 3,762,011; and European Patent EP1715274A2. According to theabove prior arts, there is no effective way to at the same time solvethe problems of size limitation, wick oxidation during manufacturing,insufficient evaporation heat transfer capability and capillary force.

Hence, the prior arts do not fulfill all users' requests on actual use.

SUMMARY OF THE INVENTION

The main purpose of the present invention is to provide a heat pipehaving an internal structure with a zeolite coating on inner surface,whereby the size of the heat pipe is limitless and wick oxidization isavoided without air isolation. Furthermore, maximum evaporation heattransfer capability and capillary force are obtained.

To achieve the above purpose, the present invention is a heat pipe withhigh efficiency, comprising a shell and a zeolite coating, where theshell has an inner surface; the inner surface surrounds an enclosedchamber; the enclosed chamber is partially filled with a working fluidunder a vacuum; the working fluid is changed into a liquid phase or agas phase by the temperature of the working fluid; the shell has anevaporator section and a condenser section; the condenser section islocated away from the evaporator section; the zeolite coating isfabricated on the inner surface; the zeolite coating is fabricated witha material comprising a zeolite, a binder and an additive; the zeoliteis mixed and stirred with the binder and the additive to obtain a slurryto be sintered on the inner surface of the shell; and the zeolitecoating has pores and each pore has a diameter from less than 10nanometers to several hundred micrometers and a specific surface of100˜600 square meters per gram (m²/g). Accordingly, a heat pipe withhigh efficiency is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood from the followingdetailed description of the preferred embodiment according to thepresent invention, taken in conjunction with the accompanying drawings,in which

FIG. 1 is the vertical cross-sectional view showing the preferredembodiment according to the present invention;

FIG. 2 is the horizontal cross-sectional view showing the zeolitesingle-layer coating;

FIG. 3 is the horizontal cross-sectional view showing the zeolitedual-layer coating;

FIG. 4 is the flow block diagram showing the fabrication of the presentinvention;

FIG. 5 is the cross-sectional view showing the zeolite coating on thesurface of the micro grooves;

FIGS. 6A-6C are views showing the zeolite crystals; and

FIG. 7 is the view of the prior art.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The following description of the preferred embodiment is provided tounderstand the features and the structures of the present invention.

Please refer to FIG. 1˜FIG. 6, which are a vertical cross-sectional viewshowing a preferred embodiment according to the present invention;horizontal cross-sectional views showing a zeolite single-layer coatingand a zeolite dual-layer coating; a flow block diagram showingfabrication of the present invention; a cross-sectional view showing azeolite coating on surface of micro grooves; and a view showing zeolitecrystals. As shown in the figures, the present invention is a heat pipe200 for cooling or recycling waste heat with high efficiency, comprisinga shell 201, and a zeolite coating 205.

The shell 201 has an evaporator section 203 and a condenser section 204located away from the evaporator section 203. The shell 201 has an innersurface 2011. The inner surface 2011 surrounds an enclosed chamber 2012.The enclosed chamber 2012 is partially filled with a working fluid 202under a vacuum, where the working fluid 202 is changed into a liquidphase or a gas phase by following a temperature of the working fluid202.

The zeolite coating 205 is formed between the inner surface 2011 and theenclosed chamber 2012 in the shell 201. The zeolite coating 205 is madeof a zeolite, a binder and an additive. The zeolite, the binder and theadditive are uniformly mixed and stirred together to be sintered on theinner surface 2011 of the shell 201.

Thus, a heat pipe with high efficiency is obtained.

The shell 201 is made of a metal having a tensile strength more than 50kilograms per square millimeter (kg/mm²) at 100˜1000 Celsius degrees (°C.); such as carbon steel, SUS201, SUS202, SUS304, SUS316 and SUS430.

The shell 201 has a cross-sectional round, elliptic, square, rectangleor polygon shape. The cross-sectional shape of the shell 201 has aradius of gyration of 1˜1000 mm and the shell 201 has a slendernessratio of 0.001˜1000.

The working fluid 202 transfers heat by being changed into a gas phaseor a liquid phase at 50˜1000° C.; and is water, an alcohol, a benzene,an alkane, a refrigerant, a synthetic oil, lithium, sodium or potassium.Or, the working fluid 202 is added with high thermally conductive powderor particles of silver, copper or aluminum.

The zeolite coating 205 has pores; and, each pore has a diameter fromless than 10 nanometers to several hundred micrometers and a specificsurface of 100˜600 square meters per gram (m²/g). The zeolite coating205 has a thickness of 1˜1000 micrometers (μm) for one layer contained.

As shown in FIG. 2, the zeolite coating 205 can be a single-layercoating of zeolite. Or, as shown in FIG. 3, the zeolite coating 205 canbe a dual-layer coating, where each layer has pores; the two layerscomprises a bottom-coating layer 207 and a top-coating layer 206sequentially formed bottom-up from the inner surface 2011; and the poresof the bottom-coating layer have larger sizes than the pores of thetop-coating layer.

A flow block diagram for fabricating the zeolite coating 205, (206, 207)is shown in FIG. 4. At first, the zeolite is mixed with the binder andthe additive for obtaining slurry. The binder is geopolymer or epoxy.The slurry is then coated on the inner surface 2011 of the shell 201.After being spread, mold formed and calcined, the zeolite coating 205 isobtained. Or, the inner surface 2011 of the shell 201 may be furtherprocessed to be roughened or to form micro grooves 2013; and, then, thezeolite coating 205 is coated on the roughened inner surface 2011 orsurface of the micro grooves 2013, as shown in FIG. 5.

The additive in the slurry is selected from aluminum oxide, titaniumoxide, zirconium oxide or silicon oxide; or a mixture of some selectedtherefrom. The zeolite framework is constructed by two tetrahedrons ofsilicon oxide (SiO₄) and aluminum oxide (AlO₄), whose form is open andhas interconnect spaces or tunnels. Thus it is a porous material with anextremely large surface for being widely used in adsorbents, catalyticconverters and catalyst carriers. The zeolite has a selectable ratio ofsilicon to aluminum, which can be low-silica zeolite,intermediate-silica zeolite or high-silica zeolite, as shown in FIGS.6A-6C. The zeolite framework type concludes MFI-type, X-type and A-type.Hence, the zeolite coating 205 of the inner surface has the followingadvantages:

(1) The zeolite coating 205 is made of a porous material. According toLaplace-Yang's formula, a capillary pressure can be obtained by thefollowing equation:

ΔPcap=(2σ·cos(θ))/rp

Therein, σ is a surface tension; θ is a contact angle of solid andliquid; rp is a pore radius. Accordingly, a smaller pore radius obtainsa greater capillary pressure. Since the radiuses of pores of the zeoliteis smaller than the micro grooves and meshes, a greater capillarypressure is obtained to increase a backflow of the working fluid 202 atthe condenser section 204 for transferring heat downwardly, upwardly,slantingly or horizontally.

(2) The zeolite coating 205 is made of a porous material. The porouszeolite coating forms reentrant cavities on the inner surface of heatpipe evaporator section 203 and act as vapor traps during nucleateboiling, which increases stable bubble nucleation sites. It alsoenlarges the heat transfer area and improves liquid replenishment. Thuspool boiling or evaporation heat transfer is enhanced.

(3) The main components of the zeolite are aluminum oxide, silicon oxideand other oxides, which will not fail by oxidation and can be innermanufactured under atmospheric conditions regardless of the size of theheat pipe.

The present invention relates to an industrial heat exchanger using pipefor cooling or recycling heat, which proposes a new design of internalstructure of the heat pipe. On using the present invention, theevaporator section 203 is contacted with heat source of corrosive gas,corrosive liquid, radioactive gas, radioactive liquid, radioactivesolid, toxic gas, toxic liquid, toxic solid, smoke, waste liquid,solvent, sludge, powder, granule, sand, incinerator bottom ash, smeltingfurnace slag, hot spring geothermal heat, steam geothermal heat, sulfurgeothermal heat or solar heat; and the heat source has a temperature of50˜1000° C. The condenser section 204 is contacted with a heat sink ofair, water, a phase-changing material or a gas-phase, a liquid-phase anda solid-phase material. The present invention applies the zeolitecoating on the inner surface of the heat pipe, where the zeolite is aporous material and has a great surface area with pore radiuses smallerthan those of micro grooves and meshes for obtaining good heat-transfercapability and capillary. The main components of the zeolite arealuminum oxide, silicon oxide and other oxides, which will not fail byoxidation; and the heat pipe, regardless of its size, can be innermanufactured under an atmospheric condition without air isolation.

To sum up, the present invention is a heat pipe for cooling andrecycling waste heat with high efficiency, where a new design ofinternal structure of a heat pipe for cooling and recycling waste heatis proposed to be inner manufactured under an atmospheric conditionwithout air isolation regardless of the size of the heat pipe.

The preferred embodiment herein disclosed is not intended tounnecessarily limit the scope of the invention. Therefore, simplemodifications or variations belonging to the equivalent of the scope ofthe claims and the instructions disclosed herein for a patent are allwithin the scope of the present invention.

What is claimed is:
 1. A heat pipe for cooling and recycling waste heat,comprising a shell, said shell having an inner surface, said innersurface surrounding an enclosed chamber, said enclosed chamber beingpartially filled with a working fluid under a vacuum, said working fluidbeing changed into a phase selected from a group consist of a liquidphase and a gas phase by following a temperature of said working fluid,said shell having an evaporator section and a condenser section, saidcondenser section being located away from said evaporator section; and azeolite coating, said zeolite coating being obtained between said innersurface and said enclosed chamber, said zeolite coating being coatedwith a material comprising a zeolite, a binder and an additive, whereinsaid binder is geopolymer or expoxy, and mixed with said zeolite andsaid additive to obtain slurry to be sintered on said inner surface ofsaid shell; and wherein said zeolite coating has pores and each pore hasa diameter from less than 10 nanometers to several hundred micrometersand a specific surface of 100˜600 square meters per gram (m²/g).
 2. Theheat pipe according to claim 1, wherein said shell is made of a metalhaving a tensile strength more than 50 kilograms per square millimeter(kg/mm²) at 100˜1000 Celsius degrees (° C.).
 3. The heat pipe accordingto claim 2, wherein said metal is selected from a group consist ofcarbon steel, SUS201, SUS202, SUS304, SUS316 and SUS430.
 4. The heatpipe according to claim 2, wherein said metal material is a mixture ofmaterials selected from a group consist of carbon steel, SUS201, SUS202,SUS304, SUS316 and SUS430.
 5. The heat pipe according to claim 1,wherein said shell has a cross-sectional shape selected from a groupconsist of a round shape, an elliptic shape, a square shape, a rectangleshape and a polygon shape.
 6. The heat pipe according to claim 1,wherein said cross-sectional shape of said shell has a radius ofgyration of 1˜1000 mm and said shell has a slenderness ratio of0.001˜1000.
 7. The heat pipe according to claim 1, wherein said workingfluid is selected from a group consist of water, an alcohol, a benzene,an alkane, a refrigerant, a synthetic oil, lithium, sodium and potassiumto transfer heat by being changed into a gas phase or a liquid phase at100˜1000° C.
 8. The heat pipe according to claim 1, wherein said workingfluid is added with nanometer sized powders or particles form of a highthermally conductive metal to obtain high heat transfer performance;said form is selected from a group consist of powder and particles; andsaid metal is selected from a group consist of silver, copper andaluminum.
 9. The heat pipe according to claim 1, wherein said zeolitecoating has only one layer and has a thickness of 100˜1000 micrometers(μm).
 10. The heat pipe according to claim 1, wherein said zeolitecoating has two layers with pores; wherein said two layers comprises abottom-coating layer and a top-coating layer sequentially obtainedbottom-up from said inner surface; and wherein said pores of saidbottom-coating layer have larger sizes than said pores of saidtop-coating layer.
 11. The heat pipe according to claim 1, wherein saidzeolite is selected from a group consist of low-silica zeolite,intermediate-silica zeolite and high-silica zeolite.
 12. The heat pipeaccording to claim 1, wherein said zeolite has a type of crystal andsaid type is selected from a group consist of MFI type, X type and Atype.
 13. The heat pipe according to claim 1, wherein said additive isselected from a group consist of aluminum oxide, titanium oxide,zirconium oxide and silicon oxide.
 14. The heat pipe according to claim1, wherein said additive is a mixture of materials selected from a groupconsist of aluminum oxide, titanium oxide, zirconium oxide and siliconoxide.
 15. The heat pipe according to claim 1, wherein micro grooves arelocated on said inner surface of said shell and said zeolite coating isobtained on surface of said micro grooves.
 16. The heat pipe accordingto claim 1, wherein said evaporator section is contacted with heatsource selected from a group consist of corrosive gas, corrosive liquid,radioactive gas, radioactive liquid, radioactive solid, toxic gas, toxicliquid, toxic solid, smoke, waste liquid, solvent, sludge, powder,granule, sand, incinerator bottom ash, smelting furnace slag, hot springgeothermal heat, steam geothermal heat, sulfur geothermal heat and solarheat; and wherein said heat source has a temperature of 50˜1000° C. 17.The heat pipe according to claim 1, wherein said condenser section iscontacted with a heat sink selected from a group consist of air, water,a phase-changing material.
 18. The heat pipe according to claim 1,wherein said condenser section is contacted with a heat sink of amaterial having a phase selected from a group consist of a gas phase, aliquid phase and a solid phase.